Newsgroups: comp.parallel.mpi
From: Marcus Dormanns <marcus>
Subject: Flow-Control in MPI
Organization: RWTH -Aachen / Rechnerbetrieb Informatik
Date: 19 Sep 1995 15:02:25 GMT
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <43mm21$9ug@news.rwth-aachen.de>

Hi everybody,

I'm just writing a program using non-blocking send operations and 
non-blocking receive operations (implemented by MPI_Iprobe and blocking
receive if a message is available). I'm developing on SUN workstations
with MPICH.
However, the send-operations need a very long time to return (in the range 
of seconds) and timing/profiling with 'UPSHOT' tells me that they only return,
if other processes succeed with a send operation or initiate a receive.
Therefore, it seems to me as if my problems might come from the flow-
control inside MPI/P4/... or an insufficient number of buffers.

Does anyone have any information regarding flow-control / buffers, or any 
other hints?

Regards,

Marcus.

----------------------------------------------------------------------------
|  _      :  Marcus Dormanns, Chair for Operating Systems
|_|_`__   :  RWTH Aachen, Kopernikusstr. 16, D-52056 Aachen
  | |__)  :  Tel.   : +49-241/80-7617  |  Fax : +49-241/8888-339
    |__)  :  e-Mail :  marcus@lfbs.rwth-aachen.de
          :  http://www.lfbs.rwth-aachen.de/~marcus/marcus.html


